Making things electronics

BASIC ELECTRONICSMedia Theory & Practice
BASIC ELECTRONICS
David Williams
& Michael Shiloh
© 2003 MakingThings LLC

OVERVIEW
Session 1
Electricity is kind of like water
The Components Inside
The Binary Miracle
Session 2
Switches can do all that?
Arrange them just right, and you have a computer
The computer does what you say millions of times a second
Reconnecting to the real world

ELECTRICITY IS LIKE WATER

LEVELS OF UNDERSTANDING
How much do you need to know?
To own a car you do not need to understand the details
of internal combustion engines, but the details leak
out : gasoline, oil, batteries
To do electronics you don't need a degree in materials
science or solid state physics, but the details
sometimes leak out : voltage, current, Ohms Law,
etc.
This session and the next are what we think you'll need
to know to begin to have an intuitive grasp over the
field of electronics.

ELECTRICITY
Think of electricity flowing like water in a pipe
The analogy to water is not perfect, but it helps.
Electrons are present and quite moveable in
every conductor.
Electricity is the ordered flow of electrons in a
conductor.

VOLTAGE AND CURRENT
Voltage is like water pressure
Measured in Volts, V
Current is like water volume
Measured in Amps, A
1/1000th
of an Amp is a milliamp – mA
Power is Voltage x Current
Measured in Watts, W
1/1000th
of a Watt is a milliwatt mW

RESISTANCE
Almost everything that conducts electricity has
a resistance. It doesn’t conduct it perfectly.
Resistance is measured in Ohms (Ω)
1000Ω = 1kΩ 1,000,000Ω = 1MΩ

OHMS LAW
Relates Voltage and Current in a simple circuit
V = I R
Volts = Current (I) x Resistance (R)
(this means I = V / R and R = V / I )

CIRCUITS – WATER AND ELECTRICITY
Electricity, like
water, flows
only when it
can.
A circuit needs a
complete path,
and a source of
energy

CIRCUIT DIAGRAMS I
Circuit Diagrams (also called Schematics) are a
compact easy way to represent circuits.
Only the essential details are represented.
Like the London Underground – drawn for
human use

CIRCUIT DIAGRAMS II
More realistic diagram
Vcc & Gnd Connections
Many paths
Chip (LM555)
Resistors, Capacitors
Nonliteral line connections
Optional parts

PRINTED CIRCUIT BOARDS
When wiringup circuits with wires is too much
work
Each trace (thin strip of copper) replaces one
wire

DEMONSTRATION CIRCUITS
Objectives
Show a simple circuit
Measure voltages & current
Materials
Battery and Lamp
Multimeter

COMPONENTS
The components that make up a circuit

CONDUCTORS
Connections are very important
Many things are conductive – car chassis / salty water
Stranded vs. Solid Core
Solid core is much more likely to break when flexed
AWG (American Wire Gauge) Standard
AWG 16 – Larger Power Connections
AWG 18 – Power Connections
AWG 22 – Good Interconnection Size
AWG 30 – Very fine – breaks easily

CELLS & BATTERIES
Chemical Reactions creating electricity
  Leadacid (car battery approx 2V)
  Alkaline (regular cells approx 1.5V)
  Lithium Ion (latest rechargeable approx 3.6V)
  Fuel Cells (new technology)
  Solar Cells (light converted into electricity)
  Fruit! (lemons with copper and zinc electrodes)
Can put them in series (end to end) to increase voltage
Can put them in parallel (side by side) to increase
current

POWER SUPPLIES
Connect to 110V AC to provide electricity in a
different form.
Be very careful with 110V! It can kill you.
Anything over 50V is dangerous.

SWITCHES AND PUSH BUTTONS
Connect and disconnect circuits

RESISTORS
As the name suggests tend to present a partial
barrier to electricity flow
Recall, Resistance is measured in Ohms (Ω)
1000Ω = 1kΩ 1,000,000Ω = 1MΩ
Also need to note rated power (e.g. 1/8W, 5W)

POTENTIOMETERS
Variable Resistors
Have a resistance that varies according to the
mechanical position of one of its wiper.

LIGHT EMITTING DIODES (LEDs)
Tiny light sources – come in a variety of colors
Require very small current – but will take all you
offer – always use a resistor! Values
between 300Ω and 1KΩ are useful.

DEMONSTRATION LEDs
Objectives
Show how to use an LED
Show how it only works one way round
Show how you need a resistor
Show how different resistors give different
brightnesses, potentiometers
Materials
Soldering iron / solder / wire
LED
Resistor / Potentiometer

CAPACITORS
As the name suggests tend to store electricity
like a minibattery
Measured in Farads (F)
0.000001F = 1µF 0.000000001 = 1pF
Also need to note rated voltage
Charging
Charge
d
Discharging

DEMONSTRATION CAPACITORS
Objectives
To show charging and discharging
capacitors
Show charge with LED / resistor
Show discharge with LED / resistor
Materials
Capacitor (large value)
2 x Resistor / LED combo
Soldering Iron, Solder

DIODES
Family of components which only let electricity
flow one way
Many different kinds – each with different
characteristics
Main characteristic to note is power (W)

DEMONSTRATION DIODES
Objectives
To show diodes blocking current
Materials
Power supply
Diode
12V Lamp
Solder / Soldering Iron

SOLENOIDS
Electromagnets
Current is passed through the coil and a
magnetic field is created
Used to release latches, lock parts in place, etc.

MOTORS
Family of components that use sequenced
electricity and magnetism to make movement
Voltage, Current, Torque & RPM often specified

RELAYS
Electromechanical Switches – Apply a current
to the coil and the connected switches are
connected and disconnected.
Cars use relays to switch 12V, 500A!
Silicon Relays also available with no moving
parts

DEMONSTRATION
SOLENOIDS / MOTORS / RELAYS
Objectives
To show solenoids, motors and relays
running
Materials
Solenoid / Motor / Relay
Power Supply

VOLTAGE DIVIDERS I
Simple and vital part of electronics. Used throughout
electronics.
Vital in the connection of sensors to computers.
Take a resistor and connect it
to a power source.
The voltage on one side is 5V,
and on the other is 0V
What would it be in the middle
of the resistor?

VOLTAGE DIVIDERS II
Can set this up:
Take two resistors of
equal value in series and
connect them to a power
source.
We can guess that the
voltage at p is 2.5V if ra = rb.
Each resistor does half
the work.

VOLTAGE DIVIDERS III
And to extend this further:
What if the resistors are
not the same?
voltage at p will be greater
than 2.5V if ra < rb. Less
resistance => less voltage
drop

VOLTAGE DIVIDERS IV
Now we have something useful
What if we substitute one
of the resistors for a
resistive sensor of some
kind?
voltage at p will be
dependent on the quality
sensed.

VOLTAGE DIVIDERS V
Variable Resistors can work like this too
With this circuit, we can
sense the rotational
position of a shaft or a
linear position
The voltage at p will be
dependent on the position
of the wiper.

DEMONSTRATION – VOLTAGE
DIVIDERS
Objectives
To mirror the foregoing voltage divider
discussion with voltage divider examples
Materials
Multimeter
Soldering Iron and Solder
Resistors
Resistive Sensors (Bend / Light)

TRANSISTORS I
Developed to switch and amplify
Come in a large number of different varieties,
shapes and sizes

TRANSISTORS II
MOSFETs are transistors that make very good
switches
A very small signal on the gate
can switch very large loads on
and off thousands of times a
second.

DEMONSTRATION – TRANSISTORS
Objectives
To show the operation of a transistor
Materials
Multimeter
Soldering Iron and Solder
Motor / Halogen
Big MOSFET
MOSFET datasheet

BINARY
The gateway to digital electronics

THE DECIMAL NUMBER SYSTEM
At the risk of stating the obvious…
We count by going through our list of number symbols
until we run out…
0, 1, 2, 3, 4, 5, 6, 7, 8, 9, …
When we run out, we mark that fact with a digit in
another column and start again
… 8, 9, 10, 11, 12, 13, 14, 15, …
When we run out again, we use another column
… 98, 99, 100, 101, 102, 103, …

THE BINARY NUMBER SYSTEM
Binary is identical, except we only have 0 and 1
We count by going through our list of number symbols
until we run out…
0, 1, …
When we run out, we mark that fact with a digit in
another column and start again
… 0, 1, 10, …
When we run out again, we use another column
… 10, 11, 100, 101, 110, 111, …

JUST LIKE A REAL NUMBERING
SYSTEM
You can convert to decimal, since you know how big
each column is – 32, 16, 8, 4, 2, 1
11002 = 1 x 8 + 1 x 4 + 0 x 2 + 0 x 1 = 1210
You can add and subtract binary numbers (and all other
arithmetical operations)
0010          1000
+ 0110              0110
1000           0010
Each column is called a bit.  Eight bits are called a
byte.

THE BIG STEP
So what’s so cool about a numbering system
that only has 2 digits?
Each digit can be unambiguously represented
by a voltage on a wire.
And you can do whatever you want with it.

83
What is 8310 or 010100112?

MATERIALS

Materials
Power Supply
1.5V Cell
Wire
Solder
Soldering Iron
LEDs
Resistors (1K & 500Ω)
Potentiometer
Diodes (highish current)
Bend Sensor
Photocell
Bend sensor
MOSFET & Datasheet
Motors
Halogens

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